1. Field of the Invention
This invention relates to optical systems and, more particularly, to systems that facilitate the alignment of optical devices.
2. Description of the Prior Art
The advancement of our civilization was and is dependent upon the ability of one generation of people to hand down to the next generation of people its knowledge and experiences. Most of the training which we receive in our lifetime is under real life conditions. For instance, an actual aeroplane is used to teach someone how to fly. An aeroplane is a complex, dangerous, and costly machine, making it highly impractical for a student pilot to receive all of his flight training in an actual aeroplane. To solve this problem, simulators have been developed to permit pilots to receive some of their flight training without leaving the ground. A simulator is a machine that duplicates, within reasonable limits, the environment, motions and malfunctions that a person would encounter while using the real machinery.
The actual equipment used in the cockpit of an aeroplane is sometimes the same equipment that is used in the cockpit of the simulator. This is done to create an environment that approximates the environment that exists in the real world. In an aircraft simulator, the cockpit of an aircraft is placed on a motion system that will move in response to the pilot's operation of the aircraft's controls, giving the pilot the sensation of motion without leaving the ground. A noise generator is also used so that the pilot will hear the same sounds that he hears while he is manipulating the controls of an actual aircraft. The pilot's visual senses must also be simulated to create a simulator that appears the same as an actual aircraft. In order for the simulator to be a useful training tool, when the pilot looks out of the window of the simulator's cockpit in order to make his final approach and land the simulated aircraft, the simulated runway must be in the same position and look the same as the actual runway does.
To create a visual impression of a scene in the real world, a person would produce a pictorial representation of that scene. An ordinary photographic picture will suffice when all the objects in the scene are standing still. However, when one of the objects in the scene is moving, a motion picture must be used in order to accurately reproduce the desired scene. The motion picture may be shown to an audience by transmitting the picture via a cathode ray tube (CRT). If the pilot looks at the picture appearing on the screen of the CRT, he will not see the same scene that he would see by looking out of the cockpit window. This is so because the objects that he is looking at are miles away and appear to be at infinity, i.e., the edge of a runway that he is flying towards. Therefore, when he moves his head left or right, up or down, the edge of the runway should not change relative to his head movements. If the pilot looked directly at the screen of the CRT, the edge of the runway would appear to move as the pilot moves his head.
An optical system has been designed to enable the pilot to see the picture appearing on the CRT screen at infinity. The aforementioned optical system comprises a spherical mirror of radius r positioned directly in front of the pilot, a beamsplitter positioned between the pilot and the center of the spherical mirror at approximately a 45.degree. angle, and a CRT located at a distance r/2 above the beamsplitter so that when the pilot looks out of the window of the cockpit, any point on the screen of the CRT will be on the image plane of the mirror, making the pilot believe that point is at infinity. In order for the pilot to believe that the objects appearing on the CRT screen are at infinity, the above optical equipment must be correctly positioned. The spherical mirror must be at a distance r equal to its radius from the normal eye position of an observer, the beamsplitter should be between the observer and the spherical mirror and form approximately a 45.degree. angle with the spherical mirror, and the CRT screen should be at a distance r /2 from the spherical mirror. A method employed by the prior art for aligning the beamsplitter and the spherical mirror consisted of clamping threaded stud plates to the spherical mirror and the beamsplitter and using an optical transit for sighting the trial and error adjustment of the bolts that are screwed into the stud plates. Thus, the alignment of the aforementioned optical system is a long and tedious process which may take several days to complete. The process of aligning the above optical system may prove to be very costly since there is a danger that the components of the optical system might be damaged in the process of aligning the sytem.